Dext Heat Recovery (DHR) had a big idea: what if they could recycle heat waste from commercial kitchens in a way that would reduce energy, costs and a kitchen’s impact on the environment?

This Lancashire and Sheffield-based collective of creative engineers knew they were on to something, but needed a technical partner to explore what was feasible. That’s where Sheffield Hallam University came in, and a series of successful collaborations have led to a working partnership that has been flourishing for almost a decade.

Heat recovery has always been challenging for the food sector, because of the difficulty of handling dirty air streams. In commercial restaurants, food is heated from chilled very quickly – which requires a lot of energy and a lot of heat – most of which is wasted. Any solution has to perform highly and overcome obstacles like grease and flame protection, while working to recover low-grade waste and reintroduce it to the system.

Early breakthroughs

It was between 2009 and 2012 that the Dext/Sheffield Hallam project team made their first technological breakthrough in heat recovery. Using state-of-the-art modelling techniques including computational fluid dynamics (CFD), a series of experimental runs and analytical engineering methods, Sheffield Hallam helped DHR develop and optimise a heat recovery plate that could be installed close to cookers and chargrills in the form of a splashback panel.

The plate absorbed waste heat and transferred it into a sealed water circuit, which was then circulated through a coil in a cylinder, providing hot water for the kitchen and substantial energy savings. The system had the advantage of performing well in difficult operating circumstances as well as being effective, robust, relatively low-cost and easy to clean.

The new technology was successfully installed in a chain of restaurants across the UK. This industry first meant that waste heat could be recovered for use in another process in the restaurant and transformed into energy, reducing commercial kitchens’ impact on the environment and their operational costs.

A new approach

The next project the team worked on was developing a second type of heat recovery system: an experimental system based in a kitchen’s air extraction duct. Our collaboration between 2012 and 2013 was a knowledge transfer partnership that employed a graduate mechanical engineer.

This project focused on the prototyping and development of a heat exchanger that could be inserted into dirty and greasy air streams inside a restaurant kitchen’s air extraction system, without a risk of system fouling or failure.

Following initial investigations, the team scoped an experimental manufacturing solution, which resulted in a prototype heat exchanger and heat pump plant. The plant recovered the waste heat from the kitchen air extractor and provided hot water, space heating and cooling for the entire restaurant.

The experimental system was successfully installed in a restaurant to evaluate its performance. But the work didn’t stop there. We then set up a consortium with Dext, William Jackson Food Group and DCI Refrigeration, and successfully applied for funding through the competitive Innovate UK Improving Food Supply Chain Efficiency. The result was a £600K project to develop a fully-fledged new heat recovery system based on the prototype.

The project is using a custom-made wind tunnel to create a comprehensive resource of test data and further validate the computational models and selection software. This novel technology has the potential to benefit the wider food and drink manufacturing industry, which presents a considerable opportunity for all.

'Sheffield Hallam seemed best suited to our needs – lateral thinkers able to work around and support our vision. The initial work exceeded our expectations and we have since established a close working relationship with the team – they are our 'go-to-guys' for any viability or improvement studies, computational modelling and business development support.'Team Dext